Issue 4803: updateUploadHistory throws when undos is empty

Source Of Truth

• GitHub issue: https://github.com/udecode/plate/issues/4803
• Title: updateUploadHistory throws an error when undos is empty
• Type: bug
• Expected outcome: avoid the crash when no matching undo batch exists, preserve intended upload history behavior, and verify with targeted coverage.

Scope

• Investigate updateUploadHistory in the media placeholder flow.
• Confirm current intent from nearby code and existing comments.
• Add the smallest sane regression test.
• Implement the minimal fix.
• Run targeted verification plus required repo checks for touched typed files.

Findings

• Issue description is concrete: findLastIndex can return -1, which makes editor.history.undos[index] undefined and batch.operations crash.
• Maintainer comment says the function exists so undo removes successfully uploaded images together instead of stepping back through placeholders.
• No obviously relevant prior solution doc surfaced from docs/solutions/.
• updateUploadHistory is exported from @platejs/media/react but consumed by the docs/template placeholder component layer, so the right regression seam is the utility spec, not the demo component.

Progress

• Fetch issue and comments
• Load task workflow skills
• Start persistent plan doc
• Read affected implementation and tests
• Add failing regression test
• Implement fix
• Verify

Verification Plan

• Targeted test for updateUploadHistory
• Build-first typecheck flow for affected package(s)
• pnpm lint:fix

Verification Results

• bun test src/react/placeholder/utils/history.spec.ts
• pnpm install
• pnpm turbo build --filter=./packages/media
• pnpm turbo typecheck --filter=./packages/media
• pnpm lint:fix
• pnpm check

ce-compound Evaluation

• Skip. This was a small defensive guard with an obvious regression seam, not reusable enough to justify a solution doc.